Ukidna – the RAVE machine

The Anglo-Australian Observatory is currently designing a new fibre positioner for the UK Schmidt Telescope. The instrument will have 2250 fibres, positioned with sub-arcsecond accuracy across a six degree field of view, and will have a reconfiguration time of one minute. The instrument is to enable the RAVE survey of high precision abundances and velocities for up to 50 million stars. The design is largely adapted from the AAO's FMOS-Echidna fibre positioner for Subaru. New design challenges for Ukidna include the enormous number of fibres, the large focal surface, and the field curvature of the Schmidt telescope. These features are mostly shared with the expected needs of future primefocus multi-fibre systems on 8-30m class telescopes. We present details and performance of the multi-actuator design.